This invention relates to a butterfly valve.
A butterfly valve is usually supplied with either a manual or an automatic control mechanism. The latter is usually an electric or pneumatic actuator, activated by a positioning sensor working from the shaft of the actuator (which shaft is coupled to the valve spindle) or from end stops, indicating the limits of travel of the mechanism. However, since the sensor is spaced apart from and not attached directly to the valve disc, after a failure of the drive system an incorrect signal as to the disc position may be generated.